Photoelectrophoretic apparatus

ABSTRACT

A photoelectrophoretic ink is spread over a flat transparent plate by a first roller traveling over the plate along a first path. Voltages are coupled to the first roller and plate and radiation is directed onto the ink for forming an image as the roller travels over the plate. A second roller travels over the plate along a path that intersects the first. The first and a third roller are used for image forming, and the second roller is used for image transferring. Web handling mechanisms are provided to feed webs between the rollers and plate as a roller moves over the plate.

United States Patent Egnaczak 1 Dec. 12, 1972 [54] PHOTOELECTROPHORETICAPPARATUS Primary Examiner-John M. Horan Attorney-James J. RalabateDavid C. Petre and 72 l t 1 nven or gay-mud K Egnaczak, WilliamsonMichael H. Shanahan [73] Assignee: )erox Corporation, Stamford, [57]ABSTRACT mm- A photoelectrophoretic ink is spread over a flat trans-[22] Filed: Oct. 28, 1970 parent plate by a first roller traveling overthe plate [21] APPL 84,714 along a first path. Voltages are coupled tothe first roller and plate and radiation is directed onto the ink p forforming an image as the roller travels over the [gill] :J.S.il ..355/3plate A second roller travels over the plate along a f i l s/G03g 5l04path that intersects the first. The first and a third 1 le 0 care I.roller are d for image g and second roller is usedfor imagetransferring. Web handling [56] Reterences cued mechanisms are providedto feed webs between the UNITED STATES PATENTS rollers and plate as aroller moves over the plate. 3,582,205 6/1971 Carreira ..355/3 Claims, 6Drawing Figures .L -23 2': g 5 n; \W

PATENTEUnzc 12 m2 SHEET 1 BF 2 3 705 7 v lllHII INVENTOR.

RAYWND K. EGN CZAP;

1 PHOTOELECTROPHORETIC APPARATUS BACKGROUND OF THE INVENTION Thisinvention relates to imaging systems and in particular to novel methodand. apparatus for the photoelectrophoretic imaging process. Even morespecifically, this invention relates to photoelectrophoretic machines.

In the photoelectrophoretic imaging process, an image is formed from animaging suspension or ink by subjecting the ink to an electric field andexposing it to activating electromagnetic radiation, e.g., light in thevisible spectrum. The imaging suspension is composed of light sensitiveparticles suspended within an insulating liquid carrier. The particlesare believed to bear a net Y electrical charge while in suspension.Conventionally, the ink is placed between injecting and blockingelectrodes used to establish the electric field and is exposed to alight image through one of the electrodes which is at least partiallytransparent. According to one theory, particles attracted to theinjecting electrode by the electric field exchange charge with theinjecting electrode when exposed to light and migrate under theinfluence of the field through the liquid carrier to the blockingelectrode. As a result of the migration, positive and negative imagesare formed on the two electrodes. The blocking electrode is covered witha dielectric material to minimize charge exchange and thereby preventthe particles from oscillating back and forth between the twoelectrodes.

The photoelectrophoretic imaging process is either monochromatic -orpolychromatic depending upon whether the light sensitive particleswithin the liquid carrier are responsive to the same or differentportions of the light spectrum. A full color polychromatic system isobtained, for example, by using cyan, magenta and yellow coloredparticles which are responsive to red, green and blue lightrespectively. An extensive and detailed description of thephotoelectrophoretic process is found in U. S. Pat. Nos. 3,384,565 and3,384,484 to Tulagin and Carreira, 3,383,993 to Yeh and 3,384,566 toClark.

Conventionally, photoelectrophoretic imaging apparatus have includedmultiple roller electrodes that travel one after the other across a flatplate electrode or alternately the plate is moved in a straight pathover first, second, third and even more rollersJThe first roller may befor electrophoretically applying an ink to the plate, the second forapplying electric field during first exposure, the third to apply anelectric field during a second exposure and the fourth for transferringan image formed over the plate electrode. Additional rol- Yet a furtherobject of the present invention is to build novel web handling means forthe photoelectrophoretic process.

Still another object of the invention is to enhance thephotoelectrophoretic process itself by performing electric fieldaveraging over the exposed photoelectrophoretic ink.

These and other objects are accomplished by a novel multiple rollerphotoelectrophoretic imaging machine wherein some rollers travel over aplate along a path at an angle to the path followed by other rollers.Altemately, a plate is moved in a first direction over one set ofrollers and in a second direction over another set of rollers. Forclarity of presentation, only the prior case is discussed in detail. Thesimplest embodiment is wherein the first set of roller(s) travel atright angles to the path followed by a second set of roller(s). All therollers have a disposable web wrapped around them between the roller andplate. The mechanism for handling the webs are carried immediately abovethe rollers and are independent of one another.

Photoelectrophoretic ink is introduced into the machine by means of adisposable film sheet having an image forming area and a rupturable podfor housing the ink. The film sheet is stretched out over the plate andthe first roller passing over it ruptures the pod to releasethe ink. Theink is then spread over the film sheet by the continuing motion of theroller.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the filmsheet employed in thepresent apparatus.

FIG. 2 is a perspective view of a pyramid rack gear used at anintersection between rack gears to permit one set of rollers to travelacross the path traveled by other rollers.

FIG. 3 is a partial side elevation view of the presentphotoelectrophoretic machine.

FIG. 4 is a plan elevation view of the present machine with the webhandling mechanisms removed.

FIG. 5 is a side sectional view of first web handling mechanisms foraset of two rollers used in the present machine.

FIG. 6 is aside sectional view of a second web handling mechanism usedin the present machine.

DESCRIPTION OF THE EMBODIMENTS FIG. 4 illustrates most of the componentsof the present machine 1. Machine 1 includes the frame 2, thetransparent flat plate 3, first and second imaging rollers 4 and 5 andtransfer roller 6. The imaging rollers are supported for travel overplate 3 by means including the imaging rack gears 8 and 9. The transferrollers are supported for travel over substantially the same area ofplate 3 by means including the transfer rack gears 10 and 11. In thespecific embodiment shown in the drawings the path followed by therollers 4 and 5 intersects the path followed by roller 6 at an angle ofabout This angle of intersection may be varied to suit the needs ofdifferent apparatus. The 90 angle is particularly advantageous becauseit allows the length of the machine to be shortened significantly;namely, by an amount proportional to the size of a roller. Furthermore,the process is enhanced because the electric fields applied between therollers and plate are averaged.

Images or copies are formed with machine 1 by spreading aphotoelectrophoretic ink over an image forming area of film sheet 13(FIG. 1) that rests on plate 3.'Conventionally, plate 3 iselectricallygrounded and the three rollers 4, 5 and 6 have high voltagescoupled to them. An image is projected to the ink on a film sheet by theexposure means 14 (FIG. 3.). The electric field established between thefirst imaging roller and plate and the activating electromagneticradiation, e.g., light in and near the visible spectrum, cause migrationof ink particles that result in the formation of a negative image onroller 4 (or a web wrapped around it) and a positive image on the filmsheet.

Alternately, the electric field applied between roller 4 and the plate 3may be used to electrophoretically deposit the particles in the ink ontothe film sheet while no radiation is being projected. The electric fieldbetween roller 5 and plate 3 is used'along with the exposure to createthe images. If the images are formed with the first roller as described,the second roller 5 is used to subject the ink image on the filmsheet'to a second exposure and electric field. This second exposure tolight and application of field improves the quality of polychromaticimages.

The transfer roller 6 has a voltage polarity that establishes anelectric field between it and plate 3 pposite in direction to that usedto form the image on the film sheet. This field attracts the inkpigments on the film sheet to the roller (or a web wrapped around it)thereby removing or transferring the ink image from the film sheet. Theelectric field and the mechanical movement of the roller 6 over theplate at the 90 intersection angle tends to offset or average outvariations in the resultant transferred image due to variations in theelectric field and the mechanical contact between roller and plate. Theaveraging can be used in forming the image also. .In this case, thefunctions of the second imaging roller and transfer roller 6 areinterchanged. The first imaging roller 4 travels over the plate 3 withlight on and voltages applied to form an ink image. Next the roller 6passes over the plate at the 90 intersecting angle to expose the inkimage and subject it to field a second time. Next the roller 5 is passedover the plate to transfer the ink image to it (or a web wrapped aroundit). A suitable mechanism is used to elevate roller 5 out of contactwith a film sheet 13 on'plate 3 when roller 4 is passed over the plateand to elevate roller 4 out of contact with a film sheet when roller 5is passed over the plate.

The photoelectrophoretic ink used to form the ink images is introducedinto the process by means of the film sheet 13. The film sheet includesa paper body 15, transparent image forming section 16 and the rupturablepod 17. The pod contains the ink and releases it when crushed by one ofthe rollers. The pod is a paper or plastic sack glued or otherwiseappropriately attached to the body 15. The transparent section is gluedor otherwise appropriately attached to body 14 over the cut-out 18 onthe side opposite the pod. it is transparent to the radiation projectedby the exposure means 14. The transparent section or sheet is on theside opposite the pod to provide a border for the image on the filmsheet when it is not transferred. The transparent sheet 16 is separatedfrom the body 6 to provide the final product. Because the ink is spreadover the transparent sheet only in areas of cut-out 18 in body 14, theborder is inherently provided for the ink image.

The film sheet is stretched out over the flat plate 3 (with pod 17facing upward) by means of the hooks 20 and 21 on either side of plate3. The film sheet has holes 22 and 23 on opposite ends that mate withthe hooks. An appropriate springbias mechanism is coupled to one set ofhooks to tightly stretch the film sheet across the plate. I v

The rollers 4, 5 and 6 are composed ofconductive metal cores havingconductive rubber wrapped around their peripheries to give goodcompliance between the rollers and plate-3. The rollers include meansfor coupling to appropriate voltage sources. Rollers 4 and 5 arejoumeled 'for' rotation in theside walls 25 and 26 of carriage 27 whiletransfer roller 6.is journeled for rotation in side walls 29 and 30 ofcarriage 31. The carriages are movably coupled to the rack gears 8-11for travel along paths defined by the rack gears.

Carriage 27 is coupled to rack gears 8 and 9 by the pinion gears 33-36.The pinion gears are mated with the rack gears and are jour-neled in theside walls of the carriage to support the carriage. The electric motor37 is mounted on the "carriage and is drivingly coupled by appropriatemeans such as pulleys and belt to pinion gears 33 and 34 for rotatingthem and propelling the carriage along racks 8 and 9 over the plate 3.The motor is reversible to allow travel in two directions over theplate.

Carriage 31 is coupled to rack gears 10 and 11 by the pinion gears -43.The pinion gears are mated with the rack gears and are journeled forrotation in the side walls of the carriage 31 to support the carriage.The electric motor is mounted on the carriage and is drivingly coupledby appropriate means such as pulleys and belt to pinion'gears 40 and 41for rotating them and propelling the carriage along racks 10 and 11 overthe plate 3. The motor 45 is reversible to allow travel in twodirections.

The rollers 4, 5 and 6 are mounted in their respective carriages atelevations relative to plate 3 to cause them to be forced by the weightof the carriage against the plate (or a web and film sheet between therollers and plate). The bearing blocks in which the rollers arejourneled may be coupled to lift or elevator mechanisms that raise orlower the elevation of the'rollers relative to the plate. The elevatorsare used to hold a roller out of contact with the plate during thecarriages travel or to urge a roller under pressure against plate 3.

' The webs and 51 shown in FIG. 5 are wrapped around rollers 4 and 5 toserve as the blocking layer during first and second imaging (exposure tolight and application of field) of ink on the film sheet. The websinclude electrically insulating materials and they are wound between thesupply reels 52 and 53 and the take-up reels 54 and 55, respectively.The supply reels have drag brakes coupled to them to maintain tension inthe webs. The take-up reels are drivingly coupled by appropriate meansto the motor 37. The web is pulled around the free rolling rollers 4 and5 at a velocity substantially equal to the translational speed of thecarriage but in the opposite direction. The webs are used to eliminatethe need to clean the periphery of the rollets.

The transfer web 57 shown in FIG. 6 is wrapped around the transferroller 6 and is the final support for the ink image formed on the filmsheet. The web '57 is wound onto the supply reel 58 and pulled therefromby the friction drive mechanism including opposed rollers 59 and 60.Roller 59 is drivingly coupled to motor 45 to pull the web 57 aroundfree rolling roller 6 at a velocity about equal and opposite to thetranslational velocity of the carriage.

The webs 50, 51 and 57 are wrapped around their respective rollers 4, 5and 6. The reels supporting the webs are coupled to the side plates ofthe carriages 27 and 31 respectively. The reels are fixedly supportedrelative to the rollers to move with them. The reels are mounted on thesame side of the rollers to obtain the wrap around and are mountedgenerally vertically above the rollers to take-up the least possibleroom. They are positioned on the opposite side of the rollers from plate3 so that they are drawn tightly against the rollers and so that if anyskid or slip between thewebs and plate occurs the webs are unlikely tobe pulled off the roller. The drive mechanism pulling the webs aroundthe rollers do so at a velocity equal and opposite to that of thecarriage to prevent skidding or slipping. The resultant web handlingmechanisms are compact, efficient and independent of one another so thatit is unlikely that one web will get in the way of another, i.e.,adversely interfere with the feeding or threading of each other.

The exposure means 14 shown in FIG. 3 includes the lamp 61, transparency62, and lens 63. This mechanism can be replaced by reflection exposuremeans for projecting an image of an opaque original. The plate 3 and thefilm sheet are transparent to the electromagnetic radiation generated bylamp 4 to allow the radiation to act on ink on the film sheet between aroller and plate. The frame 2 includes the cut-out 64 to permit theradiation image pattern to reach the plate 3.

The plate 3 includes transparent plate glass having a transparentconductive layer such as tin oxide on its side facing the rollers. Theconductive layer is normally coupled to electrical ground.

The carriages 27 and 31 are able to intersect each others path becauseof the pyramid gears placed at the intersections of the rack gears. Theisolated, perspective view of intersection 65 (FIG. 2) is representativeof the three other intersections. Sections of rack gears 8 and 11 arecut-out at the vicinity of the intersection of gears 8 and 11 and theremoved pieces are replaced by the pyramid gear 66. Each rack gearincludes a body 67 having the triangular cross-secti0n, linear teeth 68.The teeth of each rack gear are identified by their height 69 and theirpeak-to-peak spacing 70, or pitch. The height and pitch of the differentgears are designed to mate with like teeth on the pinion gears 33-36 and4043. The height and pitch are generally the same for all gears in thisembodiment but may vary one from the other in different embodiments.

The pyramid gear is formed from a member having teeth similar in heightand pitch to one of the rack gears. The teeth of this member are thencut by a tool at the desired intersection angle as if the teeth of aheight and pitch of the other rack gear were being made. For the presentcase wherein the rack gears intersect at about 90 and the height andpitch of the teeth on each rack are generally identical, the resultantmachined part resembles the pyramid gear 66 shown in FIG. 2. Gear 66 ischaracterized by the square based pyramid shaped teeth 71. The pyramids71 have a height and peak-to-peak separation (in the directions of thetwo racks) that permit the pinion gears 33 and 34 to run over it on rack8 and pinion gears 40 and 41 to run over it on rack 1 1.

The rack gears are seated in the grooves -83 cut into the frame 2. Thegrooves are laid out in a tic-tactoe pattern with horizontal grooves 80and 81 intersecting the vertical grooves 82 and 83 (as seen in the planview of FIG. 4). The rectangular cross-section of the grooves (FIG. 3)is designed to mate with the cross-sectional shape of the rack gears.The pyramid gears are positioned at the intersections of the groovesmeaning that each rack gear is separated into'three pieces. For clarityof presentation the rack gears are discussed as continuous membersbecause the pyramid gears in fact enable them to function as if they arecontinuous.

Other modifications to the above described invention will be apparent tothose skilled in the art and are intended to be incorporated herein.

What is claimed is: 1. Photoelectrophoretic imaging apparatus comprisingat least first and second roller electrodes supported for travel over aplate electrode with at least one roller traveling in a direction tointersect over the plate the path followed by at least one other roller,

means for coupling voltage sources to said plate and said rollers toestablish electric fields between said rollers and said plate, and Iexposure means for exposing photoelectrophoretic ink between a rollerand plate to activating electromagnetic radiation to create images fromink exposed to radiation and subjected to field.

2. The apparatus of claim 1 further including a blocking web wrappedaround said first roller and wound between feed and take-up reels, saidweb being wound onto the take-up reel at a velocity about equal andopposite to the velocity of the roller as it travels over said plate.

3. The apparatus of claim 2 further including a transfer webwrappedaround said second roller, wound on a supply reel and pulled therefromby drive rollers, said drive rollers capable of pulling the transfer webaround the second roller at a velocity about equal and opposite to thevelocity of the second roller as it travels across the plate.

4. The apparatus of claim 1 including first, second and third rollerelectrodes with the first and second roller electrodes following thesame path over the plate having voltages coupled to them for formationof an image and for a second exposure of the formed image and with thethird roller traveling across the plate along a path intersecting thepath of the first and second rollers and having a voltage source coupledto it for transferring an image from the plate toward the third roller.

5. The apparatus of claim 4 wherein the path of the third rollerintersects the path of the first and second rollers at an angle of about6. The apparatus of claim 1 including at least first, second and thirdroller electrodes with said first and second rollers supported to travelthe same path and the third roller supported to travel a pathintersecting the path of the first and second rollers wherein said firstroller has a voltage coupled to it for electrophoretically depositingparticles in a photoelectrophoretic ink over said plate, wherein saidsecond roller has a voltage coupled to it for forming an image fromelectrophoretically deposited ink and wherein said third roller has avoltage coupled to it fortransferring an ink image from the plate towardthe thirdroller. 7. The apparatus of claim 1 including at least first,second and third roller electrodes with said first and second rollerssupported to travel the same path and the third roller supported totravel a path intersecting the path of the first and second rollerswherein said first roller has a voltage source coupled to it for formingan image from photoelectrophoretic ink, wherein said third roller has avoltage coupled to it for a second exposure of the formed ink to saidradiation and wherein said second roller has a voltage coupled to it fortransferring a twice exposed ink image from the plate toward the secondroller.

8. The apparatus-of claim 6 wherein blocking webs (3) are wrapped aroundsaid first and second rollers between feed and take-up reels for eachweb with motor means coupled to said take-up reels to pull the blockingwebs from their feed reels past said rollers at a velocity about equaland opposite to the velocity of the rollers as they travel over saidplate.

9. The apparatus of claim 8 further including a transfer web wrappedaround said third roller and coupled to means for pulling the transferweb around the third rollerat a velocity about equal and opposite to thevelocity of the third roller as it travels over the plate.

10. Photoelectrophoretic imaging apparatus comprising a first electrodeand at least one roller electrode supported for movement relative toeach other,

feed and take-up reels positioned on the same side of said roller andopposite to the side of the roller adjacent said first electrode andfixedly supported relative to the roller electrode,

a web wound between said reels and wrapped around said roller betweenthe roller and first electrode, means for coupling voltages between saidelectrodes to establish an electric field, and means for exposing aphotoelectrophoretic ink between said electrodes to activatingelectromagnetic radiation to form an image.

11. The apparatus of claim 10 wherein said roller coupling voltagepotentials to said first and secondv electrode to establish an electricfield across said ink whereby images are formed from ink exposed tolight and subjected to field.

13. The process of claim 12 wherein said second path intersects thefirst path at an angle of about 14. The process of claim 12 wherein saidrollers move over a stationary plate electrode.

15. The process of claim 12 wherein said plate moves over stationaryfirst and second rollers.

1. Photoelectrophoretic imaging apparatus comprising at least first andsecond roller electrodes supported for travel over a plate electrodewith at least one roller traveling in a direction to intersect over theplate the path followed by at least one other roller, means for couplingvoltage sources to said plate and said rollers to establish electricfields between said rollers and said plate, and exposure means forexposing photoelectrophoretic ink between a roller and plate toactivating electromagnetic radiation to create images from ink exposedto radiation and subjected to field.
 2. The apparatus of claim 1 furtherincluding a blocking web wrapped around said first roller and woundbetween feed and take-up reels, said web being wound onto the take-upreel at a velocity about equal and opposite to the velocity of theroller as it travels over said plate.
 3. The apparatus of claim 2further including a transfer web wrapped around said second roller,wound on a supply reel and pulled therefrom by drive rollers, said driverollerS capable of pulling the transfer web around the second roller ata velocity about equal and opposite to the velocity of the second rolleras it travels across the plate.
 4. The apparatus of claim 1 includingfirst, second and third roller electrodes with the first and secondroller electrodes following the same path over the plate having voltagescoupled to them for formation of an image and for a second exposure ofthe formed image and with the third roller traveling across the platealong a path intersecting the path of the first and second rollers andhaving a voltage source coupled to it for transferring an image from theplate toward the third roller.
 5. The apparatus of claim 4 wherein thepath of the third roller intersects the path of the first and secondrollers at an angle of about 90*.
 6. The apparatus of claim 1 includingat least first, second and third roller electrodes with said first andsecond rollers supported to travel the same path and the third rollersupported to travel a path intersecting the path of the first and secondrollers wherein said first roller has a voltage coupled to it forelectrophoretically depositing particles in a photoelectrophoretic inkover said plate, wherein said second roller has a voltage coupled to itfor forming an image from electrophoretically deposited ink and whereinsaid third roller has a voltage coupled to it for transferring an inkimage from the plate toward the third roller.
 7. The apparatus of claim1 including at least first, second and third roller electrodes with saidfirst and second rollers supported to travel the same path and the thirdroller supported to travel a path intersecting the path of the first andsecond rollers wherein said first roller has a voltage source coupled toit for forming an image from photoelectrophoretic ink, wherein saidthird roller has a voltage coupled to it for a second exposure of theformed ink to said radiation and wherein said second roller has avoltage coupled to it for transferring a twice exposed ink image fromthe plate toward the second roller.
 8. The apparatus of claim 6 whereinblocking webs (3) are wrapped around said first and second rollersbetween feed and take-up reels for each web with motor means coupled tosaid take-up reels to pull the blocking webs from their feed reels pastsaid rollers at a velocity about equal and opposite to the velocity ofthe rollers as they travel over said plate.
 9. The apparatus of claim 8further including a transfer web wrapped around said third roller andcoupled to means for pulling the transfer web around the third roller ata velocity about equal and opposite to the velocity of the third rolleras it travels over the plate.
 10. Photoelectrophoretic imaging apparatuscomprising a first electrode and at least one roller electrode supportedfor movement relative to each other, feed and take-up reels positionedon the same side of said roller and opposite to the side of the rolleradjacent said first electrode and fixedly supported relative to theroller electrode, a web wound between said reels and wrapped around saidroller between the roller and first electrode, means for couplingvoltages between said electrodes to establish an electric field, andmeans for exposing a photoelectrophoretic ink between said electrodes toactivating electromagnetic radiation to form an image.
 11. The apparatusof claim 10 wherein said roller electrode and said reels fixedlysupported relative thereto are supported for travel over an area on saidfirst electrode.
 12. A photoelectrophoretic process comprising exposingphotoelectrophoretic ink on a transparent plate electrode to activatingelectromagnetic radiation, moving a first roller electrode and saidplate relative to one another along a first path, moving a second rollerelectrode and said plate relative to one another along a second pathintersecting the first path, coupling volTage potentials to said firstand second electrode to establish an electric field across said inkwhereby images are formed from ink exposed to light and subjected tofield.
 13. The process of claim 12 wherein said second path intersectsthe first path at an angle of about 90*.
 14. The process of claim 12wherein said rollers move over a stationary plate electrode.
 15. Theprocess of claim 12 wherein said plate moves over stationary first andsecond rollers.